1. Field of the Invention
Embodiments of the claimed invention relate to conveyor belt systems, and in particular, to a link member having a curved bearing surface for connecting adjacent rods of a conveyor belt system.
2. Description of Related Art
Conveyor belt systems are used in various industrial fields for material handling and processing purposes. For instance, conveyor systems are used within food processing systems in which food items are placed on the support surface of a conveyor belt and processed, while being conveyed from one location to another. Various types of conveyor belts exist, including modular conveyor belts, which are especially popular in food processing systems. Moreover, conveyor systems are often used in a helical accumulator such as that disclosed in U.S. Pat. No. 5,070,999 to Layne et al. which allows storage of a large number of items in the conveyor system.
One type of conveyor belt system comprises transverse rods connected by links disposed along the opposite transverse edges of the belt. For example, the belt can have generally U-shaped nestable links with slotted holes that allow the links to slide on the rods. The relative sliding action between the links and rods provides lateral flexibility which enables the belt to turn right or left, when such nestable links are used on both sides of the belt. When such a belt proceeds around a lateral curve, the rod ends along the inside concave edge of the belt collapse. The opposite transverse ends of the rods along the outside convex edge of the belt either remain at the same pitch as when the belt travels in a straight line direction, such as disclosed in U.S. Pat. No. 3,225,898 to Roinestad, or expand to a greater pitch in order to allow the belt to proceed around a smaller radius, as disclosed in U.S. Pat. No. 4,078,655 to Roinestad and U.S. Pat. No. 4,867,301 to Roinestad et al., each of which is herein incorporated by reference in their entireties. These types of conveyor belts are often referred to as grid-type belts. FIG. 1 illustrates a conventional grid-type conveyor belt as in U.S. Pat. No. 3,225,898 to Roinestad. FIG. 2 illustrates a conventional smaller-radius grid-type conveyor belt as in U.S. Pat. No. 4,867,301 to Roinestad et al.
Another type of conveyor belt system comprises rows of pickets with repeated bends formed from a flat strip of metal. A plurality of cross rods connect adjacent rows of pickets through openings therein. The openings can be circular and similar in radius to the cross rods so as to create a noncollapsible belt configured for straight travel. Alternatively, the openings can be slotted so as to create a collapsible belt configured for both straight travel of the belt and travel around lateral curves, such as disclosed in U.S. Pat. No. 4,846,339 to Roinestad, herein incorporated by reference in its entirety. These types of conveyor belts are often referred to as flat wire conveyor belts. FIG. 3 illustrates a conventional flat-wire conveyor belt as in U.S. Pat. No. 4,846,339 to Roinestad.
FIG. 4 illustrates a spiral low tension conveying system 100 of the type shown in U.S. Pat. Nos. 4,078,655 and 3,348,659. Since the low tension system is fully described in these patents, which are herein incorporated by reference in their entireties, only a brief description will be given here. In such a low tension system 100, a cage type driving drum 102 frictionally engages the inner edge of a conveyor belt 10 to drive it with relatively low tension through a helical path around the drum. In addition, a positive sprocket drive 104 engages the belt 10 along a straight portion thereof. A motor 105 drives the drum 102 through gearing 106 and also drives the positive sprocket drive 104 through interconnected gearing 107. The belt 10 travels from the sprocket drive 104, past weighted tension take up roller 110 and idler pulleys 111 to a straight loading portion 108, then in helical loops around the drum 102 to a straight discharge portion 109 and around another idler 111 back to the drive sprocket.
FIG. 5 is a cutaway view of a conveyor belt comprising a conventional link having a curved bearing surface, such as that described in U.S. Pat. No. 4,932,925 to Roinestad et al., which is herein incorporated by reference in its entirety. As seen in FIG. 5, each leg portion 28A has a pair of holes 34A, 35A for receiving adjacent rods 12A and 12A′. Hole 35A, which is adjacent to its respective connecting portion 30A, is in the form of an elongate slot, which allows rod 12A to move from a collapsed position during straight line conveying, to an expanded position during conveying about lateral curves. Holes 34A and 35A are positioned at a proximal end and a distal end, respectively, of their respective leg portion 28A.
As shown in FIG. 5, connecting portion 30A connects leg portion 28A to another leg portion (not shown). Connecting portion 30A has a curved bearing surface 32A between first and second side surfaces, 36A and 36A′, respectively. In this embodiment, curved bearing surface 32A substantially mates with the outer surface of rod 12A, i.e., curved bearing surface 32A has substantially the same radius as rod 12A. First and second side surfaces 36A and 36A′ extend perpendicular to leg portion 28A.
Because side surfaces 36A and 36A′ expand perpendicular to leg portion 28A within opening 35A, a corner is created in connecting portion 30A between curved bearing surface 32A and side surfaces 36A and 36A′. When link 16A turns tangentially in the expanded position, such as about a roller (e.g., roller 110 of FIG. 4), rod 12A can be forced from curved bearing surface 32A back into opening 35A. This causes rod 12A to jump the corner and creates a potentially objectionable noise. FIG. 6 illustrates this situation in which rod 12A has jumped the corner due to link 16A—s tangential movement about roller 40.